This invention relates to the conversion of thermal energy to mechanical energy via a working fluid.
The necessity to spare power and to use new power sources leads to develop processes for the production of mechanical power, which can be used as such or converted to electrical power, from heat sources of low thermal level, thus in a temperature range from, for example, 50.degree. to 400.degree. C. These heat sources may be of different nature: industrial thermal wastes, heat transmitted through solar collectors, geothermal water, etc. These heat sources can be used to generate mechanical power by means of a Rankine cycle using a working fluid which vaporizes under pressure while receiving heat from the heat source, expands while producing mechanical power, for example, in a turbine, this mechanical power being used as such or converted to electricity, and condenses when contacted with a refrigerant fluid, such as water or air.
The yield of the cycle can be improved and the use of very low pressures avoided by replacing water, a fluid which is commonly used at higher temperatures, with a fluid whose boiling temperature and critical temperature are much lower, such as butane or ammonia.
A fluid of this type vaporizes and condenses at a substantially constant temperature.
It is a rule that the temperature of the external fluids with which the exchanges are effected varies during the exchange.